Image display device that can display high brightness and high contrast images and includes a cured resin layer

ABSTRACT

A thin image display device is provided which is free from display defects caused by the deformation of an image display part and can display high brightness and high contrast images. The image display device includes an image display part, a light-transmitting protective part arranged on the image display part, and a cured resin layer interposed between the image display part and the protective part. The cured resin layer has a light transmittance in the visible region of 90% or more and a refractive index (nD) of 1.45 or more and 1.55 or less.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/909,943 filed Jun. 23, 2020, which is a continuation of U.S.application Ser. No. 16/216,525 filed Dec. 11, 2018 (now U.S. Pat. No.10,725,329), which in turn is a continuation of U.S. application Ser.No. 14/721,748 filed May 26, 2015 (now U.S. Pat. No. 10,216,026), whichin turn is a continuation of U.S. application Ser. No. 12/450,232 filedSep. 17, 2009 (now abandoned), which in turn is a U.S. national stageapplication of PCT/JP2008/057024 filed Apr. 9, 2008, which claims thebenefit of JP 2007-102252 filed Apr. 9, 2007, JP 2007-186360 filed Jul.17, 2007, and JP 2008-005027 filed Jan. 11, 2008, the contents of eachof these applications being incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an image display device such as aliquid crystal display device (LCD) used, for example, in a cellularphone, and in particular to an image display device that includes atransparent protective part arranged on an image display part and acured resin layer arranged between the image display part and theprotective part.

BACKGROUND ART

One conventional example of such an image display device is a liquidcrystal display device 101 shown in FIG. 4 .

This liquid crystal display device 101 includes a transparent protectivepart 103 made of, for example, glass or plastic on a liquid crystaldisplay panel 102, as shown in FIG. 4 .

In this display device, to protect the surface of the liquid crystaldisplay panel 102 and a polarizing plate (not shown), a spacer 104 isarranged between the liquid crystal display panel 102 and the protectivepart 103 to form a gap 105 between the liquid crystal display panel 102and the protective part 103.

However, the gap 105 present between the liquid crystal display panel102 and the protective part 103 causes light scattering, and thisresults in a reduction in contrast and in brightness. In addition, thepresence of the gap 105 also makes it difficult to produce thinnerdisplay panels.

In view of the above problems, a technique has been proposed in whichthe gap between the liquid crystal display panel and the protective partis filled with a resin (for example, Patent Document 1). However, thestress during cure shrinkage of the cured resin causes deformation ofoptical glass plates sandwiching the liquid crystal of the liquidcrystal display panel. This results in display defects such asirregularities in the orientation of the liquid crystal material.

-   [Patent Document 1] Japanese Patent Application Laid-Open No.    2005-55641.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

The present invention has been made in view of the problems in theconventional technologies. It is an object of the present invention toprovide a thin image display device which is free from display defectscaused by the deformation of an image display part and can display highbrightness and high contrast images.

Means for Solving the Problems

To achieve the above object, the present inventors have conductedextensive studies and found that as the difference in refractive index(ΔnD) between the protective part and gap of an image display deviceincreases, the brightness and contrast of the image display device arelowered due to the scattering and attenuation of image light from theimage display part. This results in a reduction in visibility. To avoidthis problem, the present inventors have found that it is effective toarrange a cured resin layer having a certain refractive index betweenthe image display part and the protective part. Thus, the presentinvention has been completed.

The inventors have also found that the internal stress accumulatedduring curing of a resin composition can be approximated by the productof the storage modulus after curing and the curing shrinkage ratio.Therefore, it is preferable to use, as the resin composition arrangedbetween the image display part and the protective part, a resincomposition that has a certain curing shrinkage ratio and yields a curedproduct having a certain storage modulus.

Accordingly, the present invention provides an image display device,comprising an image display part and a light-transmitting protectivepart arranged on the image display part, wherein

the image display device further comprises a cured resin layer arrangedbetween the image display part and the protective part, and

the cured resin layer has a light transmittance in a visible region of90% or more and a refractive index (nD) of 1.45 or more and 1.55 orless.

Preferably, in the present invention, the cured resin layer has anelastic modulus at 25° C. of 1.0×10⁷ Pa or less.

Preferably, in the present invention, the cured resin layer is a curedproduct of a resin composition having a curing shrinkage ratio of 5% orless.

Preferably, in the present invention, the cured resin layer has arefractive index (nD) of 1.51 or more and 1.52 or less.

In the present invention, the image display part may be a liquid crystaldisplay panel.

In the present invention, the protective part may be formed from anacrylic resin.

In the present invention, the protective part may be formed from anoptical glass.

Effects of the Invention

In the present invention, the cured resin layer arranged between theimage display part and the protective part has a light transmittance of90% or more and a refractive index (nD) of 1.45 or more and 1.55 or lessand more preferably, for example, 1.51 or more and 1.52 or less. In thismanner, as compared to the case in which air having a refractive indexof 1.0 is arranged therebetween, the differences in refractive index atthe interface of the image display part and the interface of theprotective part are smaller, so that the scattering and attenuation ofimage light from the image display part can be reduced. Therefore,according to the present invention, the brightness and contrast of thedisplayed image can be increased, whereby the visibility can beimproved.

In the present invention, the use of a resin composition having a curingshrinkage ratio of 5% or less and yielding a cured product having astorage modulus at 25° C. of 1.0×10⁷ Pa or less can minimize theinfluence of the stress during cure shrinkage of the resin on the imagedisplay part and the protective part. Therefore, almost no distortionoccurs in the image display part and the protective part.

Accordingly, a high brightness and high contrast image can be displayedwithout display defects.

In particular, when the image display part is a liquid crystal displaypanel, display defects such as irregularities in the orientation of theliquid crystal material can be reliably prevented, so that a highquality image can be displayed.

Moreover, in the present invention, the gap between the image displaypart and the protective part is filled with the cured resin. Thisprovides high impact resistance.

In addition, an image display device thinner than the conventionalexample in which a gap is formed between the image display part and theprotective part can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating the main part of anembodiment of an image display device according to the presentinvention.

FIG. 2 is a cross-sectional view illustrating the main part of anotherembodiment of the image display device according to the presentinvention.

FIG. 3 is a cross-sectional view illustrating the main part of anotherembodiment of the image display device according to the presentinvention.

FIG. 4 is a cross-sectional view illustrating the main part of aconventional display device

DESCRIPTION OF REFERENCE NUMERALS

1 image display device, 2 display part, 3 protective part, 4 spacer, 5cured resin, 6 and 7 polarizing plate

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of the present invention will bedescribed in detail with reference to the drawings. In the drawings, thesame reference numerals denote the same or like elements.

FIGS. 1 and 2 are cross-sectional views illustrating the main parts ofembodiments of an image display device according to the presentinvention. The display device 1 of each embodiment includes: an imagedisplay part 2 that is connected to a driving circuit (not shown) anddisplays an image in a predetermined manner; and a light-transmittingprotective part 3 that is arranged so as to face the image display part2 with a predetermined distance therebetween, as shown in FIGS. 1 and 2.

No particular limitation is imposed on the image display device, and theimage display device can be applied to various applications. Examples ofthe image display device include liquid crystal display devices for acellular phone, a portable game device, and the like. The image displaypart 2 of each embodiment may be the liquid crystal display panel ofsuch a liquid crystal display device.

When the image display part 2 is a liquid crystal display panel,polarizing plates 6 and 7 are provided on the surfaces of the liquidcrystal display panel, as shown in FIG. 2 .

When the body of the liquid crystal display panel is formed from anoptical glass, the refractive index (nD) thereof is generally 1.49 to1.50. Some tempered glass has a refractive index (nD) of about 1.55.

The protective part 3 is a plate-, sheet-, or film-likelight-transmitting member having substantially the same size as the sizeof the display part 2. For example, optical glass or plastic (an acrylicresin, such as polymethyl methacrylate, or the like) can be suitablyused as the light-transmitting member. An optical layer such as ananti-reflective film, a shielding film, or a viewing angle control filmmay be formed on the front or rear surface of the protective part 3.

When the protective part 3 is formed from an acrylic resin, therefractive index (nD) thereof is generally 1.51 to 1.52.

The protective part 3 is arranged on the display part 2 through a spacer4 provided on a peripheral part of the display part 2. The spacer 4 hasa thickness of about 0.05 to about 1.5 mm, so that the distance betweenthe surfaces of the image display part 2 and the protective part 3 ismaintained at about 1 mm.

To improve the brightness and contrast, a frame-like shielding part (notshown) is provided on the peripheral part of the protective part 3.

A cured resin layer 5 is arranged between the image display part 2 andthe protective part 3. This cured resin layer 5 has a lighttransmittance in the visible region of 90% or more. Preferably, thecured resin layer 5 is formed so as to have a thickness of 50 to 200 μm.

Preferably, the cured resin layer 5 has a refractive index (nD)substantially the same as those of the image display part 2 and theprotective part 3. More specifically, the refractive index (nD) is 1.45or more and 1.55 or less, and preferably 1.51 or more and 1.52 or less.In this manner, the brightness and contrast of the image light from theimage display part 2 can be increased, so that the visibility can beimproved.

The cured resin layer 5 has a storage modulus at 25° C. of preferably1.0×10⁷ Pa or less, and more preferably 1×10³ to 1×10⁶ Pa. Typically,even when the main resin component constituting the curable resincomposition is the same, if a remaining resin component or monomercomponent to be used is different, the cured resin formed by curing sucha curable resin composition may have a storage modulus (25° C.)exceeding 1×10⁷. Such a cured resin layer is not preferred.

The cured resin layer 5 is a cured product of a resin composition havinga curing shrinkage ratio of preferably 5% or less, more preferably 4.5%or less, and still more preferably 4.0% or less, and most preferably 0to 2%. In this manner, the internal stress that builds up in the curedresin layer when the curable resin composition is cured can be reduced,and the occurrence of distortion at the interface between the curedresin layer 5 and the liquid crystal display panel 2 or the protectivepart 3 can be prevented. Therefore, when the resin composition isarranged between the liquid crystal display panel 2 and the protectivepart 3 and then cured, the cured product can reduce light scattering atthe interface between the cured resin layer 5 and the liquid crystaldisplay panel 2 or the protective part 3. This can improve both thebrightness of the displayed image and the visibility.

The magnitude of the internal stress that builds up in the cured productof a resin composition during curing can be evaluated by the averagesurface roughness of the cured resin obtained by dropping the resincomposition onto a flat plate and curing the dropped resin composition.For example, 2 mg of a resin composition is dropped onto a glass oracrylic plate and cured by irradiation with UV light to a cure ratio of90% or more. When the average surface roughness of the resultant curedresin is 6.0 nm or less, the interfacial distortion caused by the curedproduct of the curable resin composition arranged between the liquidcrystal display panel 2 and the protective part 3 is practicallynegligible. With the curable resin composition used in the presentinvention, the average surface roughness can be preferably 6.0 nm orless, more preferably 5.0 nm or less, and still more preferably 1 to 3nm. Therefore, the distortion at the interfaces of the cured resin ispractically negligible.

Any glass plate used for sandwiching the liquid crystal of a liquidcrystal cell or used as the protective plate of a liquid crystal cellmay be preferably used as the above glass plate. Any acrylic plate usedas the protective plate of a liquid crystal cell may be preferably usedas the above acrylic plate. The average surface roughness of such glassand acrylic plates is typically 1.0 nm or less.

It is preferable from the viewpoint of improving productivity that theresin composition forming the cured resin layer 5 is a photocurableresin composition. To prepare the resin composition such that the curedresin layer 5 has a refractive index (nD) of 1.51 or more and 1.52 orless, the monomer of the resin composition is selected.

Preferred examples of such a resin include a resin compositioncontaining: at least one kind of polymer, such as a polyurethaneacrylate, a polyisoprene acrylates or an ester thereof, a hydrogenatedterpene resin, and a butadiene polymer; at least one kind of acrylatemonomer, such as isobornyl acrylate, dicyclopentenyloxyethylmethacrylate, and 2-hydroxybutyl methacrylate; and a photopolymerization initiator such as 1-hydroxy-cyclohexyl-phenyl-ketone.

The protective part 3 often has a UV cut function to protect the displaypart 2 from UV light.

In such a case, it is preferable to use, as the photo polymerizationinitiator, a photo polymerization initiator that can initiate curing inthe visible region (for example, trade name: SpeedCure TPO, product ofNihon SiberHegner K. K.).

In a method of producing the image display device 1 of each embodiment,for example, the spacer 4 and a projecting bank portion (not shown) arefirst provided on the peripheral part of the image display part 2, and apredetermined amount of the above-described photocurable resincomposition is dropped to the inner region surrounded by the spacer 4and the projecting bank portion.

Then, the protective part 3 is placed on the spacer 4 of the imagedisplay part 2, and the gap between the display part 2 and theprotective part 3 is completely filled with the resin composition.

Subsequently, the resin composition is irradiated with UV light throughthe protective part 3 to thereby cure the resin composition. In thismanner, the target image display device 1 is obtained.

In this image display device 1, since the refractive index of the curedresin layer 5 is substantially the same as that of the protective part3, the brightness and contrast can be increased, so that the visibilitycan be improved.

Since the influence of the stress during cure shrinkage of the resin onthe image display part 2 and the protective part 3 can be minimized,almost no distortion occurs in the image display part 2 and theprotective part 3. Therefore, no deformation occurs in the image displaypart 2, so that a high brightness and high contras image can bedisplayed without display defects.

Moreover, since the gap between the image display part 2 and theprotective part 3 is filled with the cured resin layer 5, high impactresistance is obtained.

In addition, the image display device 1 can be produced thinner than theconventional example in which a gap is provided between the imagedisplay part and the protective part.

The present invention can be embodied in other various forms. Forexample, an image display device 1 having no spacers 4 may be producedas shown in FIG. 3 . In this case, the above-described photocurableresin composition is applied to a base 2, and the protective part 3 isplaced on the applied resin composition. The resin composition is curedwith light in the same manner as described above.

Moreover, the present invention is applicable not only in the liquidcrystal display device described above, but also in various paneldisplays such as an organic EL, a plasma display apparatus and the like.

EXAMPLES

Hereinafter, the present invention will be specifically described by wayof Examples and Comparative Examples, but the invention is not limitedto the following Examples.

Example 1

50 Parts by weight of polyurethane acrylate (trade name: UV-3000B,manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 30 partsby weight of isobornyl acrylate (trade name: IBXA, manufactured by OsakaOrganic Chemical Industry Ltd.), 3 parts by weight of aphotopolymerization initiator (trade name: IRGACURE 184, manufactured byCiba Specialty Chemicals Inc.), and 1 part by weight of aphotopolymerization initiator (trade name: SpeedCure TPO, manufacturedby Nihon SiberHegner K.K.) were kneaded using a kneader to prepare aresin composition of Example 1.

Example 2

70 Parts by weight of an ester compound formed from a maleic anhydrideadduct of polyisoprene polymer and 2-hydroxyethyl methacrylate, 30 partsby weight of dicyclopentenyloxyethyl methacrylate, 10 parts by weight of2-hydroxybutyl methacrylate, 30 parts by weight of a hydrogenatedterpene resin, 140 parts by weight of a butadiene polymer, 4 parts byweight of a photopolymerization initiator, and 0.5 parts by weight of aphoto polymerization initiator for visible light were kneaded using akneader to prepare a resin composition of Example 2.

Example 3

100 Parts by weight of an ester compound formed from a maleic anhydrideadduct of polyisoprene polymer and 2-hydroxyethyl methacrylate, 30 partsby weight of dicyclopentenyloxyethyl methacrylate, 10 parts by weight of2-hydroxybutyl methacrylate, 30 parts by weight of a hydrogenatedterpene resin, 210 parts by weight of a butadiene polymer, 7 parts byweight of a photopolymerization initiator, and 1. 5 parts by weight of aphotopolymerization initiator for visible light were kneaded using akneader to prepare a resin composition of Example 3.

Example 4

70 parts by weight of an ester compound formed from a maleic anhydrideadduct of a polyisoprene polymer and 2-hydroxyethyl methacrylate (tradename: UC-203, manufactured by Kuraray Co., Ltd.), 30 parts by weight ofdicyclopentenyl oxyethyl methacrylate (trade name: FA512M, manufacturedby Hitachi Chemical Co., Ltd.), 10 parts by weight of 2-hydroxybutylmethacrylate (trade name: Light Ester HOB, manufactured by KyoeishaChemical Co., Ltd.), 30 parts by weight of a hydrogenated terpene resin(trade name: Clearon P-85, manufactured by Yasuhara Chemical Co., Ltd.),35 parts by weight of a butadiene polymer (trade name: Polyoil 110,manufactured by Zeon Corporation), 5 parts by weight of aphotopolymerization initiator (trade name Irgacure 184D, manufactured byCiba Specialty Chemicals Inc.), and 2 parts by weight of aphotopolymerization initiator (trade name SpeedCure TPO, manufactured byNihon SiberHegner K.K.) were kneaded using a kneader to prepare a resincomposition of Example 4.

Comparative Example 1

50 Parts by weight of polybutadiene acrylate (trade name: TE-2000,manufactured by Nippon Soda Co., Ltd.), 20 parts by weight ofhydroxyethyl methacrylate (trade name: Light Ester HO, manufactured byKyoeisha Chemical Co., Ltd.), 3 parts by weight of a photopolymerizationinitiator (Irgacure 184, manufactured by Ciba Specialty Chemicals Inc.),and 1 part by weight of a photopolymerization initiator (trade name:SpeedCure TPO, manufactured by Nihon SiberHegner K.K.) were kneadedusing a kneader to prepare a resin composition of Comparative Example 1.

Comparative Example 2

50 parts by weight of polyurethane acrylate (trade name: UV-3000B,manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), 30 partsby weight of tricyclodecane dimethanol acrylate (trade name: NK EsterLC2, manufactured by Shin-nakamura Chemical Co., Ltd.), 3 parts byweight of a photopolymerization initiator (Irgacure 184, manufactured byCiba Specialty Chemicals Inc.), and 1 part by weight of aphotopolymerization initiator (trade name: SpeedCure TPO, manufacturedby Nihon SiberHegner K.K.) were kneaded using a kneader to prepare aresin composition of Comparative Example 2.

Comparative Example 3

50 parts by weight of polybutadiene acrylate (trade name: TE-2000,manufactured by Nippon Soda Co., Ltd.), 20 parts by weight of isobornylacrylate (trade name: IBXA, manufactured by Osaka Organic ChemicalIndustry Ltd.), 3 parts by weight of a photopolymerization initiator(Irgacure 184, manufactured by Ciba Specialty Chemicals Inc.), and 1part by weight of a photopolymerization initiator (trade name: SpeedCureTPO, manufactured by Nihon SiberHegner K.K.) were kneaded using akneader to prepare a resin composition of Comparative Example 3.

Evaluation 1

The resin compositions prepared in Examples 1 to 4 and ComparativeExamples 1 to 3 were measured for light transmittance, storage modulus,curing shrinkage ratio, surface roughness, refractive index, andbrightness as follows. The results are shown in Table 1.

[Preparation of Samples]

The resin compositions prepared in Examples 1 to 4 and ComparativeExamples 1 to 3 were dropped onto a 100 μm-thick white glass plate so asto have a predetermined thickness. The glass plates were conveyed onto aUV conveyer to obtain cured products of the resins having apredetermined thickness. These serve as samples for measuring lighttransmittance, storage modulus, and curing shrinkage ratio.

[Light Transmittance]

The light transmittance in the visible region was measured for eachsample (the cured resin thickness of 100 μm) using an UV-visiblespectrophotometer (V-560, manufactured by JASCO Corporation) and wasfound to be 90% or more for all the samples.

[Storage Modulus]

The storage modulus (Pa) (25° C.) was measured for each sample at ameasurement frequency of 1 Hz using a viscoelastometer (DMS 6100,manufactured by Seiko Instruments Inc.).

[Curing Shrinkage Ratio]

The specific gravities of the uncured resin solution and the cured solidproduct were measured using an electronic densimeter (SD-120L,manufactured by Mirage Co., Ltd.), and the curing shrinkage ratio (%)was calculated by the following equation based on the difference in thespecific gravities between the uncured resin solution and the curedsolid product.Curing shrinkage ratio (%)={(Cured product specific gravity−Resinsolution specific gravity)/(Cured product specificgravity)}×100  [Equation 1][Surface Roughness]

2 mg of each resin composition was dropped onto a glass plate for aliquid crystal cell. Then, the distortion (Ra: average surfaceroughness) in a predetermined region (2.93 mm×2.20 mm) of a glass platesurface caused by the internal stress during UV curing was measuredusing a three-dimensional non-contact surface roughness metermanufactured by Zygo Corporation.

[Refractive Index]

Each resin composition was interposed between two releasing PET filmsand formed into a film shape using a spacer having a thickness of 100μm. This was conveyed on a UV conveyer to cure the resin between thefilms. Subsequently, the releasing PET films were removed. The curedresin was cut into pieces of appropriate size, and the cut pieces wereused as samples.

The sample of each cured resin was measured for refractive index using arefractometer (Model-3, manufactured by ATAGO Co., Ltd.).

[Brightness]

The image display device shown in FIG. 2 and including a protective partmade of an acrylic resin (refractive index (nD)=1.52) was produced usingeach resin composition. Then, a black pattern was displayed on the imagedisplay part in the presence of an external light source (500 to 600lux), and the brightness (brightness distribution) of the displayedblack pattern was measured. The measurement of the brightness of theblack pattern determines the quality of the contrast.

TABLE 1 Average Storage Curing surface Refractive Transmittance modulusshrinkage roughness index Brightness (%) (Pa) ratio (%) (nm) (nD)(cd/m²) Example 1 90 or more 1 × 10⁶ 4.5 5.5 1.47 10 or less Example 290 or more 1 × 10⁴ 1.8 2.7 1.52 10 or less Example 3 90 or more 4 × 10³1.0 1.5 1.52 10 or less Example 4 90 or more 4 × 10⁵ 3.8 5.0 1.52 10 orless Comparative 90 or more 2 × 10⁷ 5.6 12.4 1.49 Uneven* Example 1Comparative 90 or more 3 × 10⁸ 4.3 36.5 1.49 Uneven* Example 2Comparative 90 or more 5 × 10⁸ 5.6 64.2 1.50 Uneven* Example 3 *Uneven:measurement was difficult due to unevenness in brightness.

As is clear from Table 1, in Examples 1 to 4, the storage modulus was4×10³ to 1×10⁶ Pa, and the curing shrinkage ratio was 1.0 to 4.5%.Therefore, the average surface roughness Ra was 1.5 to 5.5 nm, andalmost no distortion occurred. The results were satisfactory. However,in Comparative Example 1 (Ra=12.4 nm), Comparative Example 2 (Ra=36.5nm), and Comparative Example 3 (Ra=64.2 nm), Ra was large. Thisindicates that the interface between the resin and the glass plate wasdeformed due to the internal stress during curing of the resin.

Moreover, in Example 1, the refractive index of the cured resin wassubstantially the same as that of the acrylic plate used as theprotective part, so that no light scattering occurred. Therefore, thevalue of the brightness was found to be good, i.e., 10 cd/m² or less.

Example 5

50 Parts by weight of polyisoprene methacrylate (trade name: UC-203,manufactured by Kuraray Co., Ltd.), 10 parts by weight of hydroxybutylmethacrylate (trade name: LIGHT-ESTER HOB, manufactured by KyoeishaChemical Co., Ltd.), 20 parts by weight of a low-molecular weightpolybutadiene polymer (trade name: Polyoil 110, manufactured by ZEONcorporation), 4 parts by weight of a photopolymerization initiator(trade name: IRGACURE 184, manufactured by Ciba Specialty ChemicalsInc.), and 1 part by weight of a photopolymerization initiator (tradename SpeedCure TPO, manufactured by Nihon SiberHegner K.K.) were kneadedusing a kneader to prepare a resin composition of Example 5.

Example 6

50 Parts by weight of polyisoprene methacrylate (trade name: UC-203,manufactured by Kuraray Co., Ltd.), 20 parts by weight of hydroxybutylmethacrylate (trade name: LIGHT-ESTER HOB, manufactured by KyoeishaChemical Co., Ltd.), 20 parts by weight of a low-molecular weightpolybutadiene polymer (trade name: Polyoil 110, manufactured by ZEONcorporation), 4 parts by weight of a photopolymerization initiator(trade name: IRGACURE 184, manufactured by Ciba Specialty ChemicalsInc.), and 1 part by weight of a photopolymerization initiator (tradename SpeedCure TPO, manufactured by Nihon SiberHegner K.K.) were kneadedusing a kneader to prepare a resin composition of Example 6.

Example 7

50 Parts by weight of polyisoprene methacrylate (trade name: UC-203,manufactured by Kuraray Co., Ltd.), 20 parts by weight of hydroxybutylmethacrylate (trade name: LIGHT-ESTER HOB, manufactured by KyoeishaChemical Co., Ltd.), 15 parts by weight of a low-molecular weightpolybutadiene polymer (trade name: Polyoil 110, manufactured by ZEONcorporation), 4 parts by weight of a photopolymerization initiator(trade name: IRGACURE 184, manufactured by Ciba Specialty ChemicalsInc.), and 1 part by weight of a photopolymerization initiator (tradename SpeedCure TPO, manufactured by Nihon SiberHegner K.K.) K.K.) werekneaded using a kneader to prepare a resin composition of Example 7.

Evaluation 2

The resin compositions prepared in Examples 1 and 5 to 7 were measuredfor light transmittance, storage modulus, curing shrinkage ratio,surface roughness, refractive index, and brightness in the same manneras in Evaluation 1. The results are shown in Table 2.

Note that, in the brightness measurement, an acrylic plate or a glassplate shown in Table 2 was used as the protective part.

TABLE 2 Average Refractive Storage Curing surface Refractive index (nD)of Transmittance modulus shrinkage roughness index protective Brightness(%) (Pa) ratio (%) (nm) (nD) part material (cd/m²) Example 5 90 or more1 × 10⁶ or less 4.5 or less 5.5 or less 1.51 Acrylic plate 1.52 10 orless Example 6 90 or more 1 × 10⁶ or less 4.5 or less 5.5 or less 1.49Glass plate 1.49 10 or less Example 7 90 or more 1 × 10⁶ or less 4.5 orless 5.5 or less 1.50 Glass plate 1.50 10 or less Example 1 90 or more 1× 10⁶ or less 4.5 or less 5.5 or less 1.47 Glass plate 1.49 10 or less

As shown above, also in Examples 5 to 7, the values of the lighttransmittance, storage modulus, and curing shrinkage ratio were similarto those in Example 1, and the average surface roughness was 5.5 nm orless. Therefore, the magnitude of distortion in the glass or acrylicplate used as the protective part was small. Moreover, in Examples 1 and5 to 7, since the refractive index of the cured resin was substantiallythe same as that of the acrylic or glass plate used as the protectivepart, practically acceptable brightness was achieved.

INDUSTRIAL APPLICABILITY

The present invention is useful as image display devices, such as liquiddisplay devices, and the like.

The invention claimed is:
 1. An image display device comprising: animage display part; a light-transmitting protective part arranged on theimage display part; a polarizing plate arranged on a surface of theimage display part; and a cured resin layer disposed on the polarizingplate and arranged between the image display part and the protectivepart, wherein the cured resin layer is a cured product of a photocurableresin composition comprising (i) at least one kind of polymer selectedfrom the group consisting of a polyurethane acrylate, a polyisopreneacrylate or an ester thereof, a hydrogenated terpene resin, and abutadiene polymer; and (ii) a photopolymerization initiator, and has: alight transmittance in a visible region of 90% or more, a refractiveindex (nD) of 1.45 or more and 1.55 or less, and a storage modulus at25° C. of 1.0×10³ to 1.0×10⁶ Pa to function as an adhesive between theimage display part and the protective part.
 2. The image display deviceaccording to claim 1, wherein the photocurable resin composition has acuring shrinkage ratio of 5% or less.
 3. The image display deviceaccording to claim 2, wherein the photocurable resin composition has acuring shrinkage ratio of 4.0% or less.
 4. The image display deviceaccording to claim 1, wherein the cured resin layer has a thickness of50 to 200 μm.
 5. The image display device according to claim 1, whereinthe cured resin layer has a refractive index (nD) of 1.51 or more and1.52 or less.
 6. The image display device according to claim 1, whereinthe photocurable resin composition further comprises at least one kindof acrylate monomer selected from the group consisting of isobornylacrylate, dicyclopentenyloxyethyl methacrylate and 2-hydroxybutylmethacrylate.
 7. The image display device according to claim 1, whereinthe image display part is a liquid crystal display panel.
 8. The imagedisplay device according to claim 1, wherein the protective part isformed from an acrylic resin.
 9. The image display device according toclaim 1, wherein the protective part is formed from an optical glass.10. A photocurable resin composition for forming a cured resin layerthat is arranged between an image display part of an image displayapparatus and a light-transmitting protective part and disposed on apolarizing plate that is arranged on a surface of the image displaypart, the photocurable resin composition comprising: at least one kindof polymer selected from the group consisting of a polyurethaneacrylate, a polyisoprene acrylate or an ester thereof, a hydrogenatedterpene resin, and a butadiene polymer; and a photopolymerizationinitiator, wherein the photocurable resin composition has a curingshrinkage ratio of 5.0% or less, and a cured resin formed by curing thephotocurable resin composition has: a light transmittance in a visibleregion of 90% or more, a refractive index (nD) of 1.45 or more and 1.55or less and a storage modulus at 25° C. of 1.0×10³ to 1.0×10⁶ Pa tofunction as an adhesive between the image display part and theprotective part.
 11. The resin composition according to claim 10,wherein the curing shrinkage ratio is 4.0% or less.
 12. A cured resinlayer arranged between an image display part of an image displayapparatus and a light-transmitting protective part and disposed on apolarizing plate that is arranged on a surface of the image displaypart, the cured resin layer being a cured product of a photocurableresin composition comprising (i) at least one kind of polymer selectedfrom the group consisting of a polyurethane acrylate, a polyisopreneacrylate or an ester thereof, a hydrogenated terpene resin, and abutadiene polymer; and (ii) a photopolymerization initiator, wherein thecured resin layer has: a light transmittance in a visible region of 90%or more, a refractive index (nD) of 1.45 or more and 1.55 or less, and astorage modulus at 25° C. of 1.0×10³ to 1.0×10⁶ Pa to function as anadhesive between the image display part and the protective part.
 13. Thecured resin layer according to claim 12, wherein the photocurable resincomposition has a curing shrinkage ratio of 5% or less.
 14. The curedresin layer according to claim 13, wherein the photocurable resincomposition has a curing shrinkage ratio of 4.0% or less.
 15. The curedresin layer according to claim 12, wherein the refractive index (nD) is1.51 or more and 1.52 or less.